Bitterblue is the daughter of Leck, the former king of Monsea, and Ashen, the former queen of Monsea and princess of Lienid. She was born in Monsea and is the heir to the Monsean throne at the start of Graceling. She later becomes the queen in Bitterblue.

She is one of the main characters in Graceling, in which Katsa absconds with her across the mountains, trying to stay out of reach of Leck. The book ends with Leck's death and Bitterblue claiming the throne of Monsea for herself. The events of Bitterblue pick up about eight years later, in Monsea. She has been very sheltered since her parents' deaths, but is trying to do a good job of ruling the country despite this.

During the course of the book, she develops close friendships with Giddon and particularly, a commoner named Saf, as well as Saf's friend Teddy and the boys' sisters, Bren and Tilda.